1. Field of the Invention
The present invention relates to an apparatus for detecting a touching position on a flat panel display, and more particularly, to an optical apparatus for detecting a touching position on a flat panel display.
2. Description of the Prior Art
A touch panel is a type of flat panel display which serves as both the input and output interface so that electronic devices incorporating it therein can perform input tasks without an additional input device. Accordingly, it has been widely utilized in the art and has become a very popular user interface (UI).
Currently, a touching position on a touch panel is detected mainly by utilizing resistive, capacitive, ultrasonic, optical principles, etc. A resistive touch panel is constituted by two transparent electrically conductive thin films spaced by a separator. When a finger presses the touch panel, the two electrically conductive thin films come in contact with each other, resulting in a change in the voltage. A sensing apparatus then senses the change in the voltage to determine the X-coordinate and Y-coordinate of the touching point on the touch panel. For capacitive touch panels, the finger is capacitively coupled to the sensing line, thus a sensing apparatus can sense the change in the capacitance to determine the X-coordinate and Y-coordinate of the touching point. For ultrasonic touch panels, the ultrasonic transmitters disposed at the three corners thereof form an even ultrasonic field. When a finger touches the touch panel, a sensing apparatus senses the change in the energy to determine the X-coordinate and Y-coordinate of the touching point.
There are a number of types of optical touch panels, including infrared touch panels, optical imaging touch panels and image recognition touch panels. For infrared touch panels, the infrared transmitters are disposed around the touch panel to form a matrix pattern, thus a sensing apparatus can sense the change in light to determine the X-coordinate and Y-coordinate of the touching point on the touch panel. For optical imaging touch panels, the shadow of a touching object is sensed by the imaging lens assemblies placed at two corners of the touch panel, and then triangulation is performed to determine the position of the touching object. As for an image recognition touch panel, it detects the image rather than the shadow of the touching object. However, the image recognition touch panel has a drawback of requiring multiple imaging lens assemblies.